1. Field of the Invention
The invention relates to a high-power radiator, especially for ultraviolet light, comprising a discharge space, which is filled with a fill-gas that emits radiation under discharge conditions, and of which the walls are formed by a first tubular dielectric and a second dielectric that is provided on its surfaces averted from the discharge space with first and second electrodes, and including an alternating current source connected to the first and second electrodes for feeding the discharge.
In this regard, the invention relates to the prior art such as follows, for example, from EP-A 054 111, from U.S. patent application 07/076,926 now U.S. Pat. No. 4,837,484 or also from EP patent application 88113393.3 dated 22 Aug. 1988 or U.S. patent application 07/260,869, dated 21 Oct. 1988, now U.S. Pat. No. 4,945,290.
2. Discussion of background
The industrial use of photochemical processes depends strongly upon the availability of suitable UV sources. The classical UV radiators deliver low to medium UV intensities at a few discrete wavelengths, such as, e.g. the low-pressure mercury lamp at 185 nm and especially at 254 nm. Really high UV powers are obtained only from high-pressure lamps (Xe, Hg), which then, however, distribute their radiation over a sizeable waveband. The new excimer lasers have made available a few new wavelengths for basic photochemical experiments, but for reasons of cost they are probably only suitable at present in exceptional cases for an industrial process.
In the EP patent application mentioned at the beginning, or also in the conference publication "Neue UV- und VUV Excimerstrahler" ("New UV and VUV Excimer Radiators") by U. Kogelschatz and B. Eliasson, distributed at the 10th Lecture Meeting of the Society of German Chemists, Specialist Group on Photochemistry, in Wurzburg (FRG) 18-20 Nov. 1987, there is a description of a new excimer radiator. This new type of radiator is based on the principle that excimer radiation can also be generated in silent electrical discharges, a type of discharge which is used on a large scale in ozone generation. In the current elements, which are present only briefly (&lt;1 microsecond), of this discharge, rare gas atoms are excited by electron impact, and these react further to form excited molecular complexes (excimers). These excimers live only a few 100 nanoseconds, and upon decay give their bond energy off in the form of UV radiation.
The construction of such an excimer radiator corresponds as far as the power generation largely to a classical ozone generator, with the essential difference that at least one of the electrodes and/or dielectric layers delimiting the discharge space is impervious to the radiation generated.
The above-mentioned high-power radiators are distinguished by high efficiency and economic construction, and enable the creation of large-area radiators of great size, with the qualification that large-area flat radiators do require a large technical outlay. By contrast, with round radiators a not inconsiderable proportion of the radiation is not utilized due to the shadow effect of the internal electrodes.